This invention relates to a method for creating a network from technical devices, such as digital electronic consumer devices and/or computers. More particularly this invention relates to technology to transmit high quality video and audio over power-line networks and a fast retransmission method to improve target packet hit rate (TPHR), where
  TPHR  =            Number      ⁢                          ⁢      of      ⁢                          ⁢      receiving      ⁢                          ⁢      packet      ⁢                          ⁢      at      ⁢                          ⁢      destination      ⁢                          ⁢      node              Number      ⁢                          ⁢      of      ⁢                          ⁢      original      ⁢                          ⁢      packet      ⁢                          ⁢      at      ⁢                          ⁢      source      ⁢                          ⁢      node      for both unicast and multicast services.
Power line communication networks have proven to be a cost-effective solution for the construction of in-building network to deliver broadband audio, video, and data services. One advantage is the low installation cost saving resulting from the usage of the existing low-voltage cable and AC outlets. The development of power line communication standards such as HomePlug AV and Open PLC European Research Alliance (OPERA) have boosted the achievable data rate up to 200 Mbps or more in the physical layer. One drawback is that the indoor power-line channel is a frequency selective fading channel with time-varying characteristics susceptible to performance degrading interference. One such source of interference is the colored and impulsive noise generated by electrical appliances and external sources. Another source of interference is the multi-path response corresponding with the power cable layout and loading conditions. Such a harsh transmission environment could cause highly unpredictable interference and damage a series of consecutive packets. Packet loss rate has been found to be small if the running traffic is light loaded, and increases significantly once the sending rate exceeds a threshold value. Such a threshold may have great variation under different connection topology or in the environment with other power appliances interference existing.
In retransmission mechanisms which take place directly between the source and destination node, such as ARQ (Auto Repeat reQuest), the receiver sends out acknowledge signal (NACK) when packet loss is found. In response, the source node is configured to transmit the requested data block. Most existing multicast protocols adopt a static retransmission scheme (unicast or multicast) to retransmit lost packets. Static unicast mode may result in great network load increase, while the multicast mode may cause accuracy variation among receivers.
In recent years, some QoS enhancement technologies for reliable video transmission through PLC network have been proposed. Most focus on the forward error control (FEC) in application layer, and the deployment of multiple description coding (MDC). The transmission efficiency of these two approaches however are affected greatly when the sending rate is higher than the threshold value, especially under the condition when packet loss rate is increasing, as these two approaches both require adding redundant information with the service stream to improve the robustness when part of the information is lost. The introducing of redundant data will add the burden of traffic load, which will lead to more severe packet loss. Therefore, the supplement of the redundant data is only suitable in the scenario when the average packet loss rate is low and enough free bandwidth is available. As far as the data integrity is considered, the retransmission mechanism is necessary and it should be deployed in any system suffered with burst or constant packet loss. When the source sending rate exceeds the threshold value, the packet loss rate increases with the augment of sending rate, and the packet loss rate has great variation among different peers. Thus, it is desirable to have a method of addressing packet loss rate while avoiding the previously stated problems.